The most widely used methanol dissociation catalysts contain copper or copper oxides in intimate association with other transition metals or their oxides, or alkaline earth metals or their oxides. The preparation of these methanol dissociation catalysts generally involves co-precipitation of all constituents (except perhaps the silica) from a common solution of their soluble metal salts (e.g., the nitrates) the product insoluble salts in intimate association as the precipitate.
The resulting precipitate is usually calcined, i.e., heated sufficiently to remove water, organic solvents and salts, and to give the catalyst a certain degree of structural integrity. Calcination is generally conducted at elevated (200.degree. C.-700.degree. C.) temperatures. Higher temperatures may cause sintering of the catalyst, with attendant loss of activity due to a reduction in surface area. An oxidizing atmosphere, e.g. air or oxygen, facilitates the conversion of various metal salts to their respective matal oxides. In many instances, the metal oxides are the catalytically active species. For other catalysts, the metal oxides may be reduced, for example with hydrogen, to form the active catalyst.
The choice of calcining atmosphere depends on the catalyst being treated. Stiles, Catalyst Manufacture, Marcel Dekker, New York, discloses that the atmosphere in which catalysts are calcined can be steam, oxygen, carbon dioxide, nitrogen, hydrogen, or carbon monoxide, but no criteria are given for choosing the best calcining atmosphere.
In some references in the prior art, the atmosphere is specified to be "air", but more commonly the nature of the calcining atmosphere used in the preparation of methanol dissociation catalysts is undefined. U.S. Pat. No. 4,431,566 discloses a process for the catalytic conversion of methanol into hydrogen and carbon monoxide using a catalyst comprised of alumina as a carrier material and nickel and potassium carried on the carrier material. Preparation of the catalyst includes calcination in an atmosphere of oxygen.